Pulse energized gas tube circuit



April 1952 E. o. JOHNSON 2,591,824

PULSE ENERGIZED GAS TUBE CIRCUIT Fil ed Jan. 2, 1951 INVENTOR EDWARD U. .T uz-msnn ATTORNEY Patented Apr. 8, 1952 UNITED STATES PATENT OFFICE Edward Oscar Johnson, Princeton, N. J assignor to Radio Corporation of America, a corporation of Delaware Application January 2, 1951,.SerialNo-203,951

8 Claims.

[.Thisinvention relates to improvements in electron gas tube systems, and particularly to an improved system for pulse energizing a gas-filled electron tube of the type wherein the functions ofioni'zation and of principal current delivery are separated.

In a copending application of the present applicant, Serial No. 185,745, filed September 20, 1950, "assigned to the'assign'eeoi the present invention, there is described a gaseous electron tube wherein ionization is accomplished by passing current between a pair of electrodes in the tube in order to permit large quantities of current to be passed between two other tube electrodes at voltages lower than that required to ionize the gas in the tube. In .acopending application of In Malter, Serial No. 203,923, filed concurrently herewith .and assigned to the assignee of the present invention, and in .a copendin'g application 'o'fI. Wolff, Serial No. 212,632, filed February23, 1951 and also assigned to the assignee of the present invention, there are described methods and'system for operating gas-filled electron tubes by means of pulse voltages. at

It is a general object of the present invention to provide an improved apparatus for pulse energization of gas -filled electron tubes.

A more specific object of the invention is the provision of an improved pulse energizing arrangement for gas-filled electron tubes which is adapted to be operated with a voltage source loiger than that required to, ionize the gas in the tu e.

An additional object of the invention is the provision of an improved automatic starting'circult for a pulsed gas tube system.

In accordance with the invention, the .foregoing and other related objects and advantages are attained in a system wherein the voltage developed across an induct r by interrupting current flow therethrough is added to the voltage of" the current source supplying the inductor in such a way as to provide voltage pulses of ampli= tude suiiicient to ionize the gas inthe tube.

A more complete und'erst'anding'o'f the invention can be had by referring to the following description of illustrative embodiments thereof, when considered in connection with the accomp'anying drawing, wherein:

Fig. 1 is a schematic diagram of an electron gas tube system arranged in accordance with the invention,

Figs. 2 and 3 are schematic diagrams of modified formsof the system shown in Fig. 1,

' Figs. '4 and 5 illustrate the structure of gas Fig. 6 is a diagram of a further embodiment of the invention.

As is explained inthe above-mentioned copending application of the present applicant, it is possible to operate a gas-filled electron tube withlow voltages and under readily controlled conditions by providing for anauxiliary discharge current in the tube to generate an ion-electron plasma which will support the main tube current. In general, 'itis necessary that thea'auxiliary discharge be established by means of 5 voltage of amplitude sufiicient to ionize" the gas in the tube. Ithas been found, however, that the ionizing discharge need not be acontinuous discharge, but that it can be discontinuous or pulsating in nature. In Fig. l of the drawing, there is shown a system for deriving ionizing pulses for a gas tube from a voltage sourceof potential less than that required to ionize the tube gas. 7 s Referring to Fig. '1, there is showna gas tube It! having an anode 12, a cathode. M, a control electrode l6, and anauxiliary electrode IBl In the-embodiment of the'invention presently being described, the auxiliary electrode l8 serves as an auxiliary anode to which electrons will flow from the cathode M to ionize the gas in the tube lll. However, as will be shown hereinaftenthe auxiliary electrode l8 can aswell comprise an'electronem'itter or cathode with slight modification of the circuit. I

The main tube anode I2 is connected to a voltage source, shown as a battery 22, through a load 26. The load 20 may comprise anyone of a number'of different elements, such asthepri' mary winding of a transformer, a loadfr esistor, or the like. The precise character of the load 26 is not material for present purposes.

The auxiliary electrode l8 also'is connectedlin circuitwith the cathode I4 through an inductor 24 and the voltage source'22. A capacitorzfi is connected in parallel with the series combination of the inductor 24 and the voltage source 22. Also, a resistor 28 is connected across the capacitor 26 i'n'series'with'a switch30. 7

Assuming that the voltage of the source 22 is less than that required to ionize the gas in the tube l 0,, it can be seen that no appreciable current will flow in the tube l0 under static conditions. However, if the switch 30 is closed briefly, current will flow through the inductor 24 and through the resistor 28. If, now, the switch 30' is opened, the efiect of suddenly interrupting the current flowing through the inductor 24 will be to develop across the inductor a voltage substantially equal to that of the source 22. Also, the polarity of this voltage across the inductor 24 will be suchas to add to the source voltage, so that the voltage between the cathode I4 and the auxiliary electrode I8 will be approximately twice the voltage of the source 22. If this total voltage between the electrodes I4, I8 is sufficient to ionize the gas in the tube I0, current will flow between the electrodes I4, I8. Also, the ionization produced by this flow of current from the cathode I4 to the electrode I8 will allow current to flow from the cathode I4 to the main anode I2 and through the load 28.

Within a short time after current flows between the electrodes I4, I8, the voltage across the inductor 24 will decrease sufficiently to stop the ionizing current flow between the electrodes I4, I8. However, current will continue to flow through the inductor 24 and into the capacitor 26, thereby setting up an oscillatory action in the inductorcapacitor circuit 24, 26. This willcause the voltage between the electrodes I4, I8 again to build up to the point necessary to ionize the gas in the tube. In this way, a periodic or pulsating current will flow between the electrodes I4, I8, at a frequency determined by the inductance of the inductor 24 and the capacitance of the capacitor 26.

, As is explained in the above-mentioned copending Malter application, if the current pulses between the cathode I4 and the electrode I8 are of sufiicient intensity and recur rapidly enough,

a substantially constant current can be drawn from the cathode I4 to the main anode I2. Furthermore, this current can be modulated by applying a modulating voltage between the control electrode I6 and the cathode I4 through input terminals 32. Thus, it becomes possible to operate the gas tube II] from a source of voltage lower'than that required to ionize the gas in the tube, and to control the tube current by means of an external control voltage.

As was previously stated, the auxiliary electrode I8 in Fig. 1 could as well comprise an auxiliary cathode. An arrangement of this type is shown in Fig. 2.

In Fig. 2 the various elements all correspond with similar elements in the circuit of Fig. 1, with the exception that the auxiliary electrode I8a in the tube III is an electron emitter rather than an electron collector. This necessitates a slight change in the circuit configuration. The polarity of the voltage source 22 remains the same so that a positive voltage will be applied between the tube anode I2 and the main cathode I4. However, the auxiliary cathode IBa is returned through the inductor 24 to the negative terminal of the voltage source 22 rather than to the positive terminal as in the circuit of Fig. 1. As in Fig. 1, a capacitor 26 is in shunt with the series combination of the voltage source 22 and the inductor 24. Also, a resistor 28 and a switch 38 are in series across the capacitor 26.

In the circuit of Fig. 2, temporary closing of the switch 30 will establish current flow through the inductor 24 and the limiting resistor 28. When the switch 30 is opened, a voltage will be developed across the inductor 24 which will add to the voltage of the source'22, making the total voltage between the auxiliary cathode IBa and the anode I2 approximately twice the source voltage. Thereupon, current will flow from the auxiliary cathode I8a to the main anode l2, ionizing the gas in the tube III. The remainder of the circuit function will be essentially the same as in the circuit of Fig. 1.

Thus far, no consideration has been given to the type of cathode I4 in the tube ID in Figs. 1 and 2. In the usual case, it is preferable to use a thermionic emitter. This, however, introduces a starting problem. Either it is necessary to provide a separate energization circuit for the cathode heater element, so that the cathode can be heated before main circuit operation is started, or some means is required for supplying circuit interrupting action after the tube cathode has reached operating temperature. In Fig. 3, there is shown a completely automatic starting circuit wherein the closing of a single switch will initiate the desired circuit action.

In the circuit in Fig. 3, the gas tube I0 is provided with a heater element I5 for the cathode I4. This heater elementis connected to the voltage source 22 through a switch 34. The cathode I4 is connected to the voltage source 22 through a holding winding 36 of a relay 38. The relay 38 has a second winding 48 which is connected in series between the voltage source 22 and a movable contact 42 of the relay. The circuit for the inductor 24 is completed through the resistor 28 and through the fixed contact 44 of the relay. A spring 4| normally biases the contact 42 against the fixed contact 44.

When the switch 34 is closed, current will begin to flow through the heater I5 to begin heating the cathode I4. Also, current will begin to flow through the inductor 24, the contacts 42, 44, the resistor 28, and the winding 40. Before the heater I5 has warmed up, very little current will flow through the holding winding 36. However, a substantial current will flow through the winding 40, causing the contacts 42, 44 to open. As soon as these contacts open, the current through the winding 40 will be cut off, and the contacts 42, 44 again will close. This action will continue, each time generating sufficient voltage at the auxiliary electrode I8 of, the tube I0 to cause an ionizing discharge. However, until the cathode I4 becomes heated no discharge will take place.

As soon as thecathode I4 becomes heated, a

current pulse will flow from the cathode I4 to the auxiliary electrode I8. Also, the current will increase. through the holding windings 38 as the heater I5 warms up, so that when the cathode I4 becomes fully heated the current through the winding 36 will-keep the contacts 42, 44 open. Thereafter, the circuit will operate in substantially the same manner as has already been described for the circuit in Fig. 1.v Although details of tube structure form no part of the present invention per se, for the sake of concreteness thereis shown in Fig. 4 a sectional view of a gas tube such as might be used in the circuits of Figs. 1 and 3. In Fig. 5 there is shown a similar view of a tube such as might be used in the circuit of Fig. 2.

The tube shown in Fig. 4 has a gas tight envelope I6, within which there is placed a cathode l4, surrounded by a mesh-type control grid I6 and, outside the grid I6, by an anode I2. An additional electrode I8 is provided adjacent to the cathode I4 to receive ionizing current therefrom. This auxiliary electrode I8 may, for example, comprise two rods disposed on opposite sides of and parallel with the cathode I4.

The tube shown in Fig. 5 comprises a gas tight envelope I0 provided with a cathode I4. A U- shaped control electrode or grid I6 and a U- gteiiiieii.

:shapedianode I 2 partially'surroun'd"themathode "I4: j'Ihe gridI 6'comprises a'pluralityef parallel wires I l'j which are supported in" space'drelation.

Opposite the open-endsof the gridf'IG and the anode IZthere is mountedan auxiliary cathode Ifia. As is explained in the above-mentionedapplication of the presentapplicant, it is advantageous'to concentrate the auxiliary cathode ionizing current by surrounding the auxiliary tion. In Fig. 6, there is shown a gas tube circuit in which the principles of the present invention are used. to advantage even though no grid control is had of the work circuit current.

'Th'eici'rcuit of Fig. 6 includes a gas-filled tube Ina of a commercialtyp'ewidely known as a 2050 thyratron, taken as typical of many similar conventional gas tubes. The tube Ilia has a cathode I4, usually heated by a filament (not shown) a control electrode I3, a so-called shield electrode I2, and an anode I8. In the circuit of Fig. 6, the shield electrode I2 actually serves as an electron collector or anode, and the anode I8 serves as an auxiliary or ionizing electrode. Therefore, these electrodes, I2 and I8, will be referred to hereinafter as the anode I2 and the auxiliary electrode 88 to conform with the functions thereof.

As in the circuits of Figs. l-3, the auxiliary electrode It in Fig. 6 is connected to the cathode I4 through an inductor 24 and a voltage source 22. Similarly, a capacitor 25 is connected in shunt with the inductor 24 and the source 22, and a resistor 28 and switch 30 are connected in series across the capacitor 26, as in Figs. 1-3.

The inductor 24 has a dual function in the circuitof Fig. 6. In addition to assisting the developmentof ionizing pulses as previously described, the inductor 24 acts as the primary winding of a transformer which has a secondary winding 21. The secondary winding 2! is connected in series with a resistor 29 between the anode I2 and the voltage source 2. A filtering capacitor 3| is connected across the resistor 29.

By closing and opening the switch 30, sufficient voltage can be built up between the cathode I4 and the auxiliary electrode I8 tocause pulse ionization as previously described. The pulsating current flowing through the inductor 24 .will induce a higher voltage in the secondary winding 21. The anode I2 will cooperate with the cathode I4 to rectifythe stepped up voltage appearing across *the secondary winding 21, providing a unidirectionalvoltage across the resistor-capacitor combination 28, 3|. This unidirectional voltage can be utilized in any suitable load' device 33 connected to a pair of output terminals 35. Thus, the'circuit of Fig. 6 will function as a D.-C. transformer.

The magnitude of the voltage available at the terminals 35 will depend largely on the turns ratio'of the transformer 25. An important advantage of the system resides in the fact that 6 through a: COTIduCfiVB'jpM'Smw"filial separately ionized" gas tube with a voltage"v dropas low ee :1 volt.

'Due to electrode configuration, the controlel'ectrode I3 in the tube Illa' willl'i'ave little control over the work'circuit'current. Thiselectrode I3 can be left disconnected or floating' as-shown. It should be noted, however, thata mesh-type control electrode surrounding the cathode I4 could be provided for workcircuit current control if desired. 7

From the foregoing, it will be seenthat the present invention provides a simple and efiicie'nt system for operating a gas-filled tube from a source of voltage less than that -r'equired to ionize thetubegas.

' What is claimed is:

l. A pulse energizing system for a gas fllle'd electron tube having a first'pair of electrodes for passing ionizing current through the tube and having a second pair of electrodes'including at least one electrode in addition-to said first pair for passing current through the gas so ionized, a source of voltage of amplitude less than that required to ionize the tube gas, an inductor, a first circuit connecting said inductor to said source to establish current flow through said inductor, a second circuit connecting said inductor and said source between said first pair of electrodes, a circuit connecting said source between said second pair of electrodes, and means to interrupt the flow of current in said first circuit to develop a voltage sufilcient to cause ionizing current flow between said first pair of electrodes.

2. A gas tube system comprising a gas-filled electron tube having a plurality of electrodes including a cathode, a source of voltage of amplitude less than that required to ionize the gas in said tube, an inductor, a circuit connecting said voltage source and said inductor in series between said cathode and another of said electrodes, a switch, a second circuit connecting said switch between said cathode andsaid another electrode,

a work circuit including" said voltage source connecting two of said electrodes including said cathode, and a capacitor connected between said lastnamed two electrodes.

3. A gas tube system comprising a gas-filled electron tube having three electrodes including an anode, a' cathode, and a third electrode, a source of voltage of amplitude less than that required to ionize the tube gas, an inductor, a circuit including said voltage source and said inductor connecting said anode and said third electrode to ionize the gas in said tube in pulses, a load device, and a "circuit separate from said first-named circuit connecting said anode to said cathode through said load device.

4. A system for operating a gas-filled tube of the type having a plurality of electrodes including a cathode electrode, said system comprising a source of voltage of amplitude less than that required to ionize the gas in said tube, a load device, a work circuit connecting two of said electrodes and including said voltage source and said load device, an inductor, a circuit including said voltage source and said inductor to generate a first voltage pulse of amplitude sufiicient to ionize said tube gas, a circuit connecting said voltage pulse generating circuit between said cathode and another of said electrodes, a capacitor, and a circuit including said capacitor, said inductor, said cathode and said another electrode to generate pulses of amplitude sufficient to ionize said tube gas subsequent to said first voltage pulse.

5. A pulse energizing system for a gasefilled electron tube having electrodes including an anode, a cathode and an auxiliary electrode, said system comprising a source of voltage of amplitude less than that. required to ionize the tube gas, an inductor, a capacitor, a pulse generating circuit connecting said auxiliary electrode and another of said electrodes and including said inductor and said voltage source, said pulse generating. circuit including a switch operable to complete a circuit through said inductor in parallel with said source, said capacitor being connectedin said pulse generating circuit in parallel with said switch, and a work circuit connecting said anode-and said cathode through said source.

6. A pulse energizing system fora gas-filled electron tube having a plurality of electrodes, said system comprising a source of voltage less than that required to ionize the gas in said tube. an inductor, a circuit connecting said voltage source and said inductor in series between two of said velectrodes, a switch, means normally biasing said switch closed, a second circuit connecting said inductor and said switch in series across said voltage source, current responsive switch actuating means connected in said second circuit for opening said switch in response to current flow through said second circuit, a heater for one of said electrodes and a circuit including said voltage source for supplying current to said heater. g

7. Apparatus as defined in claim 6 wherein said switch actuating means and said switch comprise a relay having a pair of contacts contreatedin said second circuit and having an operating wind-ing connected in said second circuit. 8. Apparatus as defined in. claim 7 wherein said relay has an additional operating winding connected in circuit with two of said electrodes and said voltage source.

EDWARD OSCAR J OHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,130,191 Meier Sept. 13, 1938 2,158,564 Meier May 16, 1939 

